When we first fall asleep, more time is spent in physically repairing sleep, and then later on during the night more time is spent in psychologically repairing sleep.

Age influences the duration and balance between these two types of sleep. Babies spend more time in psychologically repairing sleep, also called a "dream state," because their bodies need little physical repair. Older adults spend more time in physically repairing sleep because their bodies are more vulnerable to damage and other stress.

The first four stages are called non-REM (rapid eye movement) sleep while the fifth stage is called REM sleep. The stages of sleep have been catecatorized into five phases.

Stage One. A transitional stage between waking and sleep where alpha waves disappear slowly, and theta waves move in. The body muscles relax, and the heart beats slower.

Stage Two. Theta waves are prominent, with intermittent sleep spindles (bursts of faster activity) and K-complexes (higher amplitude activity).

Stage Three . This is the stage where deep sleep first begins. It is characterized by the appearance of large slow delta waves, which are most dominant in the next phase; stage four.

Stage Four. Delta waves dominate. The sleeper breathes deeply and has slowed heart rate and lowered blood pressure. Stage four is deep sleep.

Stage Five. Characterized by rapid eye movements (REM), absence of muscle tone, and mixed frequency EEG. This is called "paradoxical sleep" because EEG activity is typical of an aroused nervous system, while the response of the sleeper to the environment is very low.

Dreams occur during non-REM and REM sleep, but we tend to remember the dreams in REM more because they are more vivid, bizarre, and emotionally laden; making them more likely to be remembered upon awakening.

Although medications are frequently prescribed to help people fall asleep, sleep medications were never designed for long term use or to be the solution to sleep problems. Medications can interfere with the natural progression through the stages of sleep, causing an unrefreshed feeling upon awakening. In addition, medications often have side effects such as drowsiness, and can create a dependency on the medication in order to sleep. Fortunately, there are complementary and alternative therapies that can help improve a person’s quality of sleep.

References
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